Featuring eight number ones and 44 Top 40 singles, Now That's What I Call Music! Vol. 73, the series' second hits compilations of 2009, is just as hit-packed as ever. Opening with four of the biggest singles of the year, Lady GaGa's infectious "Poker Face," David Guetta's summer anthem "When Love Takes Over," Calvin Harris' '90s trance-inspired "I'm Not Alone," and Cascada's synth-heavy "Evacuate the Dancefloor," the first disc only confirms how successful the dance-pop genre has recently become. Elsewhere, Chipmunk and Tinchy Stryder represent the emerging British hip-hop scene with their breakthrough hits, the feisty rock-pop of P!nk's "Please Don't Leave Me" is matched by newcomers the Veronicas and Katy Perry, while tracks from Take That and Girls Aloud only highlight why they are currently the U.K.'s two premier pop groups. The stand-out tracks, however, are Pussycat Dolls' Bollywood crossover "Jai Ho!," Jordin Sparks' epic power ballad "Battlefield," and La Roux's surprise electro-pop hit "In for the Kill." The second disc is dominated by American R&B with Black Eyed Peas' minimal techno number one "Boom Boom Pow," Ciara and Justin Timberlake's funky "Love Sex Magic," and Flo Rida's-Eiffel 65 sampling "Sugar" the highlights. Elsewhere, 3OH!3 and Kasabian provide the album's only rock-led tracks, Florence and the Machine,Little Boots, and Noisettes all justify their initial critical acclaim, while the triple whammy dance chillout of Empire of the Sun, DeadMau5, and Chicane is the perfect way to close a much more varied second half. Now 73 may not be as eclectic as some of its predecessors, but as dance-pop and R&B are currently conquering the upper reaches of the charts, it's undoubtedly a fair representation of 2009's musical climate.